The present invention relates to video tape recording apparatus and methods providing control of recording commencement at the tape top.
Each of FIGS. 1 and 2 illustrates a respectively different mechanical tape deck in which an 8-mm tape cassette 100 has been mounted and from which a magnetic tape 102 has been drawn from a cassette shell 104 and wrapped around a rotary drum 106 thereof. As shown in FIGS. 1 and 2, an infrared generating unit 62 produces infrared light which is projected toward an infrared sensing unit 61 across the tape 102. The magnetic tape 102 includes a transparent leader portion at the beginning thereof followed by a real (recordable) magnetic tape portion. Since the leader portion is transparent, light from the unit 62 passes therethrough to the sensing unit 61, but is interrupted by the real tape portion when it intervenes between units 61 and 62.
In each of FIGS. 1 and 2, a border position 63 representing the position at which the leader portion joins the real tape portion of the magnetic tape 102, is detected by the infrared sensing unit 61 and the infrared generating unit 62. It will be seen that the distance along the tape 102 from the position 63 to a portion thereof wrapped around the drum 106, referred to as run-in portion 64 differs in the case of the tape decks shown in FIGS. 1 and 2.
The 8-mm VTR has a system controller which commences recording upon detection of the border position 63 by means of the units 61 and 62. Since the distance between the tape run-in portion and the border position 63 in the case of the mechanical deck of FIG. 1 is longer than that produced by the mechanical deck of FIG. 2, the recording area of the magnetic tape 102 in the case of the mechanical deck of FIG. 1 begins at a point further from the border position 63 than in the case of the mechanical deck of FIG. 2. This result is illustrated by FIGS. 3A and 3B which show, respectively, a recording area 67 of the tape 102 recorded by the mechanical deck of FIG. 1 and a recording area 67' of the tape 102 as recorded by the mechanical deck of FIG. 2.
As will be seen from FIGS. 3A and 3B, when a tape which has been recorded by the mechanical deck of FIG. 2 is reproduced by the mechanical deck of FIG. 1, portion 66 of the recording area 67' in FIG. 3B will not be reproduced. In addition, when a tape which has been recorded by the mechanical deck of FIG. 2 is later re-recorded by the mechanical deck of FIG. 1, and the re-recorded tape is thereafter reproduced by the mechanical deck of FIG. 2, the signals recorded in the area 66 cannot be reproduced.
These problems are common among 8-mm VTR's of various types, as well as VHS-system VTR's, Beta system VTR's and the like. The principal cause of these problems is that the various mechanical decks use different loading systems. Further loading systems of still other VTR's are illustrated in FIGS. 4A, 4B and 4C, by way of example.